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Level C

Vol. 24, No. 12

Floods Dangerous Water


es Just 6 inch can r te a w moving n down. o rs e p a knock

broken levee

Danger – flood warning! Floods can harm people, animals, buildings, and crops. Just eighteen inches of water can carry a car away! Flood water can be only several inches high, or reach the tops of houses. In the United States, about 130 people die in floods each year. Throughout the world, floods kill more people each year than hurricanes (hur-ri-canes), volcanoes (vol-ca-noes), and lightning combined.

What Causes Floods? Floods happen when land that is normally dry gets covered with water. Some of the worst floods occur when rivers overflow. This can happen after heavy rain or from quickly melting snow. Strong winds and heavy rain from hurricanes can raise the sea level many meters, causing ocean floods. Flash floods can develop quickly after heavy rain. The soil and plants can’t absorb all the water from the storm. Flash floods can be especially dangerous because they happen with little warning. Even a small stream or creek can flood and suddenly become deadly.

houses on stilts

flash flood from melting snow

Protecting Against Floods Dams and levees (le-vees) can help stop rivers from flooding. Sea walls can protect people and buildings from floods in coastal (coast-al) areas. Some houses are built on stilts to keep them dry in case of a flood. Sometimes, a dam or levee can fail. During Hurricane Katrina in 2005, the sea level rose around 25 feet. The levees that surrounded New Orleans broke, and the city flooded. After two years, many homes and businesses ruined by flooding still have not been rebuilt. C-1

Vocabulary Fill in the blanks. The letters in the yellow boxes will spell another word for sea wall. 1. A structure built across a river to control floods


Many bridges in where there ar places e floods have lo lots of ud alar ms that go of f whe na is about to flo river od.

2. Houses are built on these to keep them dry during floods 3. Hurricane that hit New Orleans 4. Huge storms with strong winds that can cause floods Another word for sea wall is:

. Adult Supervision Recommended

Weekly Lab

How do dams and sandbags help people control water and protect from floods? Build a dam and make some sandbags. Use your science journal. Do you think the clay or the sandbags will work better? Which do you think will control water flow better? Write your hypothesis. You need: a meat loaf pan, modeling clay, old children’s socks, sand, rubber bands, water 1 2 water Step 1: Using the modeling clay, make a dam down the center of the meat loaf pan. Make it almost as high as the top of the pan. Step 2: Fill one side of the pan with water. Did your dam keep the water on one side? Step 3: Now press your thumb into the clay to make an indentation. What happened? Step 4: Empty the pan. Make sandbags by filling the socks with sand. Step 5: Wrap rubber bands around the socks as shown. Step 6: Stack the socks tightly around the sides of the pan extending above the top of the pan. Step 7: Fill the pan with water. Now add some more. How did your sandbags work?

clay, pan





rubber bands


socks water


SCIENCE WEEKLY, Level C (ISSN 8756-1778), March 21, 2008 is published monthly in August, November, December, February, April and May; and, twice-monthly in September, October, January and March. Copyright Š 2008 (Level C) CAM Publishing Group., Inc., 2141 Industrial Pkwy., Suite 202, Silver Spring, MD 20904-7824 U.S.A. (301) 680-8804 (800) 4-WEEKLY. Classroom subscription rate: (minimum 20 subscriptions to same address): $4.95 per student, per school year. Individual rate for orders less than 20 subscriptions: $19.95 per student, per year, payable in advance. Periodical postage paid at Silver Spring, Mar yland and additional mailing of fices. Postmaster: Send address changes to Science Weekly, Level C, P.O. Box 70638, Chevy Chase, MD 20813-0638. Visit our web site at C-2

Math The strong winds and heavy rains of hurricanes often cause floods. Floods are expensive. After floods, homes, buildings, and roads may need repairing. Look at the circle graph below to answer the questions. 1. What was the total amount of damage from the hurricanes? Katrina $125 billion

Rita $ 16 billion Charley $ 15 billion

Wilma $ 16 billion

2. What was the amount of damage from the hurricanes other than Katrina? 3. What hurricane caused 7 times more damage than Dennis?

Dennis $ 2 billion Ivan $ 14 billion Frances $ 9 billion

Writing in Science What supplies would you need to have if a flood were predicted where you live? What steps could you take to keep safe? Write a paragraph explaining what you would do if a flood were coming.

Now check the web site of Federal Emergency Management at: to find their recommendations.


Published by CAM Publishing Group, Inc., Silver Spring, MD • Publisher / Editor, DR. CLAUDE MAYBERRY, JR. • • Associate Editor, DR. LAURA GEHL • Writer, TRICIA ACTON • Artist, LINDA KING • Graphic Design and Production, LINDA KING • • Materials in this issue may not be reproduced in whole or in part in any form without special permission from the publisher.


Challenge Some states have lots of flooding each year. Some states have less. It is expensive to rebuild after floods damage cities and towns. Look at the map, below, then answer the following questions. You may need extra paper. 1. Which states have the most flood damage each year? 2. Which states have the least flood damage? Flood Costs in Millions by State

$85.73 to $156.8

$197.8 to $682.3

$27.3 to $65.06

$0.47 to $18.38

3. Find your state on the map. Do you live in a state with lots of flooding? Average per Year spent on Flood Damage by State (Millions) Source: Center for Science and Technology Policy Research, Data based on most current available

Puzzle Solve the rebus to find out something to do if a flood is coming.


DID YOU KNOW?? The waves of a tsunam i can travel at 800 kilometers (496 miles) per hour.

a tsun Waves from er 40 can reach ov ) high. et fe 1 3 (1 meters

“What do a yo-yo, a swing, and a baseball bat have in common?” “They are all pendulums!” “You will learn about pendulums in our next issue.” C-4

Science Weekly Floods Level C  

Science Weekly Floods Level C

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